A gas sensor includes a p-type semiconductor layer that contains copper or silver cations and contacts with detection target gas, a first electrode that is a Schottky electrode to the p-type semiconductor layer, a high-resistance layer that is provided between the p-type semiconductor layer and the first electrode such that the p-type semiconductor layer and the first electrode partly contact with each other and has resistance higher than that of each of the p-type semiconductor layer and the first electrode, and a second electrode that is an ohmic electrode to the p-type semiconductor layer.